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Vector Library Operator Index [] in C++ Programming Language
Vector Library Operator Index [] in C++
Access element. Returns a reference to the element at position n in the vector container.
A similar member function, vector::at, has the same behavior as this operator function, except that vector::at is bound-checked and signals if the requested position is out of range by throwing an out_of_range exception.
Portable programs should never call this function with an argument n that is out of range, since this causes undefined behavior.
Syntax for Vector Operator Index [] in C++
#include <vector>
reference operator[] (size_type n);
const_reference operator[] (size_type n) const;
n
Position of an element in the container. Notice that the first element has a position of 0 (not 1). Member type size_type is an unsigned integral type.
Function returns the element at the specified position in the vector.
If the vector object is const-qualified, the function returns a const_reference. Otherwise, it returns a reference.
Member types reference and const_reference are the reference types to the elements of the container (see vector member types).
Complexity
Constant
Iterator validity
No changes
Data races
The container is accessed (neither the const nor the non-const versions modify the container). The reference returned can be used to access or modify elements. Concurrently accessing or modifying different elements is safe.
Exception safety
If the container size is greater than n, the function never throws exceptions (no-throw guarantee). Otherwise, the behavior is undefined.
/* Returns a reference to the element at specified location pos. No bounds checking is performed. Unlike std::map::operator[], this operator never inserts a new element into the container. Accessing a nonexistent element through this operator is undefined behavior. */
/* Access element from a vector by vector::operator[] code example */
#include <iostream>
#include <vector>
int main ()
{
std::vector<int> myvector (10); // 10 zero-initialized elements
std::vector<int>::size_type sz = myvector.size();
// assign some values:
for (unsigned i=0; i<sz; i++) myvector[i]=i;
// reverse vector using operator[]:
for (unsigned i=0; i<sz/2; i++)
{
int temp;
temp = myvector[sz-1-i];
myvector[sz-1-i]=myvector[i];
myvector[i]=temp;
}
std::cout << "myvector contains:";
for (unsigned i=0; i<sz; i++)
std::cout << ' ' << myvector[i];
std::cout << '\n';
return 0;
}
Program print all the possible combination of each length from the given array in gray code order. The 'time complexity' of this algorithm is 'O(n*(2^n))'. This algorithm takes the input
Code sample about C++ language Function overloading. If a "C++ Class" have multiple member functions, having the same name but different parameters and programmers
